Paper sheets are made by dewatering a pulp suspension, forming a uniform web, and drying the web. During the papermaking process, various chemicals are commonly added to increase the productivity and also enhance paper physical properties. For example, retention/drainage aids are added to the pulp suspension to increase the pulp dewatering rate and also fix the anionic substances to the final paper sheet. Paper strength resins are also often introduced to increase paper dry strength and/or wet strength.
Glyoxylated polyacrylamide (GPAM) is generally used in a variety of paper grades to enhance the dry and temporary wet strength. It is used for example to increase the initial wet strength of many household tissues which come in contact with water in use. Glyoxylated polyacrylamide is also applied to increase the compression strength and the dimensional stability of many board-grade paper products.
Cationic glyoxalated polyacrylamide is a well-known strength resin that is often regarded as benchmark for generating dry strength. The polyacrylamide backbone normally incorporates a small amount of a cationic monomer, e.g. diallyldimethyl ammonium chloride (DADMAC), rendering the polymer self-retaining on fibers. GPAM is a reactive polymer that can covalently bind with cellulose upon dehydration.
U.S. Pat. No. 8,435,382 discloses a glyoxylated polymer obtained from the reaction between glyoxal and a cationic polyacrylamide base polymer comprising at least about 25% by weight cationic monomer. U.S. Pat. No. 8,435,382 also discloses a process of making paper which comprises absorbing an amount of the glyoxylated polyacrylamide polymer on cellulose papermaking fibers in aqueous suspension, forming said suspension into a water-laid web and drying said web, wherein the amount of glyoxylated polyacrylamide polymer is effective to increase at least one paper property selected from dry strength, wet strength, or de-water rate.
US2010/0326615 discloses a process for making paper comprising adding silicon-containing microparticles and a glyoxalated polyacrylamide polymer comprising at least about 25% by weight cationic monomer to an aqueous suspension containing cellulosic fibers, and forming said suspension into a water-laid web and drying said web to form paper. Before dewatering, the fiber suspension treated with the combination of GPAM polymers and silicon containing microparticles can have one or more optional additional additives mixed into the fiber suspension such as flocculants and coagulants.
US2011/0056640 discloses a process for improving drainage in paper making comprising adding an effective amount of a cationic GPAM to the aqueous suspension of cellulosic fibers, wherein the GPAM product is prepared using a basepolymer comprising greater than 10 mole-% of cationic monomer.
It would be beneficial to develop a chemical program to increase both papermaking retention/drainage rate and also paper strength properties. Such 2-in-1 program would simplify the management of chemicals significantly, resulting in less operator errors. In addition, such program would also lower the cost of chemicals and also the pumping equipment.